Identification and phosphorylation site mapping of a sperm specific PKA C subunit isoform from Mytilus galloprovincialis

ABSTRACT: This project investigates a sperm-specific isoform of the catalytic (C) subunit of cAMP-dependent protein kinase (PKA) in the marine mussel Mytilus galloprovincialis, an externally fertilizing invertebrate widely used as a model for gamete activation studies. A C-subunit isoform purified from male gonadal tissue was identified by LC–MS/MS as the protein corresponding to UniProt entry A0A8B6GIP6. Sequence analysis revealed high structural conservation with mammalian Cα2 within the catalytic core, but also demonstrated the presence of a markedly extended, acidic N-terminal region unique to mussel sperm. Comprehensive phosphoproteomic profiling identified phosphorylation at Ser5 and Thr30 within the N-terminal extension, as well as a likely regulatory phosphosite at Thr200 located in the activation loop of the kinase catalytic core. Phosphorylation events detected in unenriched samples were independently validated through TiO₂ phosphopeptide enrichment followed by LC–MS/MS. These findings reveal structural and regulatory motifs not present in mammalian sperm PKA isoforms and suggest the existence of molluscan-specific mechanisms controlling sperm activation.

INSTRUMENT(S):

ORGANISM(S): Crenomytilus

SUBMITTER: Susana Bravo  

LAB HEAD: Susana B Bravo

PROVIDER: PXD076788 | Pride | 2026-09-07

REPOSITORIES: Pride